The present invention relates to electrical measurements and, in particular, to precision AC measurements.
It is common to use an analog-based auto balance bridge technique in precision AC impedance measurements. In such measurements, a voltage signal is applied to one terminal of an impedance and an analog feedback loop is used at the second terminal to zero out any resulting voltage at the second terminal. The current provided by the loop is measured to determine the current through the impedance resulting from the voltage signal, and hence, the impedance is determined by the ratio. Because the second terminal is at a virtual ground, the measurement technique eliminates the effects of, for example, stray capacitances to ground, as there is no potential difference between the virtual ground and the actual ground.